Aerial refueling is the process of transferring fuel from one aircraft to another during flight. Aerial refueling is used to prolong the amount of time an aircraft can remain airborne, and may also allow an aircraft to take-off with a larger payload by reducing the weight of the fuel onboard the aircraft during take-off. After take-off, the aircraft can then be topped off with fuel.
One refueling system in use today for aerial refueling is a hose-and-drogue system. Another refueling system is a flying boom system. For the hose-and-drogue system, a tanker configured uses a drogue (similar to a windsock) at the end of a refueling hose. During refueling operations, the tanker un-reels the refueling hose off of a hose reel to deploy the hose and the attached drogue. A receiver aircraft to be refueled guides a probe on the aircraft into the drogue. Once mated, the tanker delivers fuel to the receiver aircraft through the refueling hose. While the hose-and-drogue system is generally less complicated to implement than a flying boom system, it delivers fuel at a lower rate than the flying boom system. The United States (US) Air force recognized this during the 1950's and switched from the hose-and-drogue system to the flying boom system to allow for large bombers to be refueled faster. However, the US Navy continues to use the hose-and-drogue system for its aircraft. The hose-and-drogue system is also used by the North Atlantic Treaty Organization (NATO).
A tanker equipped with the flying boom system uses a boom coupled to the back of the tanker to deliver fuel. The boom is attached to the tanker using a joint at the tanker end that is free to move. The boom also has flight control surfaces that allow an operator on the tanker to effectively “fly” the boom into position for refueling a receiver aircraft. Once in position, the operator deploys a refueling tube from the end of the boom that mates with a receptacle on the receiver aircraft. Once mated, the tanker delivers fuel to the receiver aircraft through the refueling tube. One example of a type of receptacle for mating with a refueling tube is a Universal Aerial Refueling Receptacle Slipway Installation (UARRSI), which is found on US Air Force aircraft. While the flying boom system is generally more complicated to implement than the hose-and-drogue system, it can deliver fuel at a faster rate than the hose-and-drogue system.
One problem encountered in providing refueling services to aircraft in mixed forces (e.g., refueling both US Air force and US Navy aircraft during the same mission) is the incompatibility between the hose-and-drogue system and the flying boom system because aircraft equipped for one system cannot be refueled by the other system. Although drogue adapters exist for the flying boom system, the use of the drogue adapter during refueling activities precludes receptacle-equipped aircraft from being refueled by flying booms that have been fitted with the drogue adapter.
In view of the above discussion, problems remain for implementing refueling systems efficiently, especially when mixed force refueling activities are performed.